Heretofore, a cotton, a foamed polyurethane or the like has been used for a seat for an automobile or train, and also for a cushion material for a medical appliance or household furniture. The foamed polyurethane is widely used since its strength can be readily changed by a foam density or a kind of a specific resin of the polyurethane, and also the foamed polyurethane has an excellence in its resilience when being compressed. The foamed polyurethane, however, may have a harmful effect on the human body when a skin of the human body makes contact with the polyurethane. The reason for this is that a residual monomer or the like in the foamed polyurethane has an irritating property with respect to the human body, the residual monomer being due to a polymerization process for the foamed polyurethane. Moreover, the foamed polyurethane does not sufficiently allow the air to pass therethrough, thereby making it undesirable to use the foamed polyurethane in some field. While on the other hand, the cotton is not involved in the problem of the residual monomer as described above. However, the cotton may be insufficient for its use as the cushion material since the fibers of the cotton tend to undergo a biased position in the use of the cushion.
There has been provided an aggregation wherein spun fibers made of thermoplastic resin such as polyester resin and the like are shaped into a form of net (see Japanese Patent Publication Nos. 5459436 and 5459438). In recent years, such aggregation has been increasingly used in various fields since it is not associated with the problems such as the irritating residual monomer and the biased position of the fibers, and also it has a sufficiency in an air permeability.